This invention relates to a gear probe, more particularly to an apparatus for testing the flank shape (involute) and flank direction (tooth orientation) of straight or helical involute gears. The apparatus has a first carriage displaceable by means of a motorized spindle drive on a stationary guide way in a direction perpendicular to the axis of the gear to be tested. On the first carriage there is mounted a linear guide way which may be angularly adjustable in a plane which is parallel to the gear axis. The gear probe further has a second carriage which is displaceable by means of a motorized spindle drive in a guide way which is parallel to the gear axis and which may be coupled to the first carriage or to the stationary guide way. On the second carriage there is mounted a measuring sensor which is set to the base circle diameter of the gear to be tested. The second carriage, by means of a sliding block, engages into the linear guide way mounted on the first carriage. The gear probe further has a third carriage which, by means of a connection with the first carriage, is movable in a direction perpendicular to the axis of the gear to be tested. On the third carriage there is mounted a linear transmission track engageable by the periphery of a transmission disc supported in axial alignment with the gear. For the purpose of mutual positioning of the gear and the measuring sensor, the linear transmission track is longitudinally displaceable with respect to the third carriage by means of a threaded spindle. Further, the transmission disc may be disengaged from the linear transmission track by a motorized drive which moves the transmission disc away from the linear transmission track.
An apparatus of the above-outlined type is disclosed in German Auslegeschrift (Application Published After Examination) No. 2,460,446. As described therein, the coupler between the first and third carriages comprises a U-shaped lever which, with its web connecting the legs of the lever, is pivotally supported on the apparatus frame. By virtue of such an arrangement it is not necessary to use a separate transmission disc which fits precisely the different base circle diameters of the gears to be tested, but it is sufficient to have transmission discs available which correspond merely to the order of magnitude of the given base circle diameter; the fine adjustment to the precise base circle diameter in each instance is obtained by changing the effective length of one of the legs of the U-shaped lever.
It is noted at this point, however, that the present invention is not limited to the particular structure of a gear probe as outlined above. Rather, the present invention may find application in other conventional gear probes of the type outlined above, wherein for each gear a transmission disc is used which corresponds precisely to the base circle diameter of the gear tested and wherein the first and third carriages are connected directly (that is, relatively unadjustably) with one another.
For testing the flank shape or the flank orientation by the gear probe disclosed in the above-identified German Auslegeschrift, it is first required to position the gear flank with respect to the measuring sensor. This is achieved by disconnecting the transmission disc from the linear transmission track and the gear to be probed is so rotated manually that it is coarsely pre-positioned for a measuring step. Thereafter, the transmission disc is brought into engagement with the linear transmission track by moving the carriage on which the transmission disc and the gear support are mounted, in the direction of the linear transmission track by a motor drive which may be push-button-operated. Then, by rotating the setting spindle of the first carriage by a motor drive and thus simultaneously causing displacement of the third carriage (on which the linear transmission track is mounted) transversely to the axis of the gear to be probed, the measuring sensor is brought next to the gear flank to be tested. Because of an only coarse previous positioning of the gear, however, the measuring sensor arrives in such a deflected position onto the gear flank that the inductive transmitter coupled with the measuring sensor and emitting measuring signals is not balanced to the zero value or even to an approximately zero value. Stated differently, the measuring sensor is in such a deflected position that for the measuring process which follows, a full scale which is of equal extent on either side of the zero position is not available. Rather, the measuring range is shifted in one direction so that in that direction only a relatively small measuring range is available as compared to the opposite direction. Thus, in order to counteract a very substantial deviation of the measuring sensor from the zero position, the transmission disc is again disconnected from the linear transmission track and the coarse position of the gear to be probed is corrected manually by appropriate rotation. If, after the first coarse positioning or after a successive coarse positioning the deviation of the measuring sensor from the zero position is only relatively slight, the linear transmission track is, with respect to its carriage (that is, the third carriage) and thus simultaneously with respect to the first carriage manually displaced by actuating a setting spindle connected therewith. Such a displacement is continued until an indicator provided for this purpose shows that the zero positioning of the measuring sensor and thus the zero equalization of the inductive transmitter connected therewith is at least approximately reached. Thereafter, by actuating the setting spindle drive coupled with the first or the second carriage the measuring process pertaining to the gear flank shape or the gear flank orientation may be carried out and the sensed measuring values typed out by a printer device.
As a rule, these measurements performed on a gear are taken for several gear flanks distributed along the circumference of the gear. Thus, for example, measurements are performed at three gear flanks in which case the gear, after each measurement, has to be stepped by approximately 120.degree.. Such stepping, in turn, is performed by manually rotating the gear after having disconnected the transmission disc from the linear transmission track, whereupon the above-described process involving a likely coarse positioning and fine positioning has to be repeated.
The above-outlined method is expensive and time-consuming particularly because of the continuously needed manual operations: since the measuring process proper is performed relatively rapidly and thus the manual adjustments take a very substantial share of the entire measuring time for the individual gears, the gear probe can be utilized for the measuring process proper only during a relatively small portion of the entire measuring time required for the gear.